Well sure Palps was going to win in the end, but it just irks me that he won because Yoda and Kenobi are literally too stupid to grasp that 2 > 1. I guess the fault lies ultimately with Lucas, who wrote it that way so that he could cut back and forth between two action packed lightsaber duels. Making sense was apparently secondary.

Mostly it is true that 2 > 1, but just look at Darth Maul. He was able to take on both Obi-Wan and Qui-Gon relatively well. This is Palpatine, and while he and Yoda may have been equals, he would be much too overwhelming for Obi-Wan, even with Yoda there, and might even get in Yoda's way.

Besides, if Obi-Wan stayed to help out Yoda, Anakin would never have been burnt to a crisp and have his legs and an arm cut off by Obi-Wan, and we wouldn't have Vader.